Basic aluminum halides and nitrates, particularly chlorides, and their use as effective antiperspirant compounds are both well-known. In general, basic aluminum halides and nitrates are complex structures made up of mixtures of polymeric and monomeric species of various sizes and molecular structures, depending upon their Al:anion ratio, together with varying amounts of bound or coordinated water. The basic aluminum compounds are generally represented by the empirical formula: EQU Al.sub.2 (OH).sub.(6-x) Y.sub.x
wherein Y is Cl, Br, I and/or NO.sub.3, and x may be between 0 and 6. It should be understood that the above formula is greatly simplified and is intended to include basic aluminum halides and nitrates containing coordinated or bound molecules of water as well as basic aluminum halide and nitrate polymer complexes and mixtures of the above.
Many attempts have been made to improve the antiperspirant efficacy and other properties of basic aluminum compounds. One school of thought that has grown in popularity is based upon improving the efficacy of basic aluminum compounds by increasing the percentage of aluminum species having a retention time corresponding to Band III of a Standard Basic Aluminum Chloride Size Exclusion Chromatogram. A number of attempts to increase efficacy have focused on processes for the production of such basic aluminum compounds.
For example, U.S. Pat. No. 4,359,456 of Gosling et al. (Unilever) discloses heating a wide range of basic aluminum halides and nitrates in a 10 to 34 wt. % aqueous solution (2.5 to 8.5 wt. % aluminum) to a temperature of 50 to 140.degree. C. for a period of time sufficient to cause the basic aluminum compound to have a Size Exclusion Chromatography Test Band having a relative retention time corresponding to Band III and a Band III aluminum value of at least 20%. The heating step is carried out for a period of from 1/2 hour to 30 days in a closed tube, bottle or reactor, followed by cooling to ambient temperature and drying to a water soluble powder. The increase of the percentage of aluminum in the Band III fraction to a level of 20% or more is said to result in an enhancement of the antiperspirant activity of the basic aluminum compound.
U.S. Pat. No. 4,775,528 of Callaghan et al. (Gillette) discloses an antiperspirant composition of zirconyl hydroxy chloride and aluminum hydroxide in a stable solid. Enhanced efficacy is reportedly achieved by heating a 2% to 20% by weight aqueous solution, containing at least the aluminum chlorhydroxide component of the composition, until the ratio of the height of the peak corresponding to Kd=0.7 (Band IV) to that of the peak corresponding to Kd=0.5 (Band III) is at least 2:1. At column 2, lines 60-61 of this patent it is disclosed that at least 80% and preferably at least 90% of the total of aluminum is present within the peaks corresponding to Bands III and IV.
U.S. Pat. No. 4,944,933 of Inward (Unilever) discloses a process for the manufacture of basic aluminum chlorides in powder form for antiperspirant use in which an Al:Cl molar ratio of 1.7:1 to 2.2:1 and a Band III fraction of at least 20% is obtained. The process of this patent comprises dissolving metallic aluminum powder in an aqueous starting solution of aluminum chloride or basic aluminum chloride having an Al:Cl molar ratio of up to 1.8:1. The starting solution is held at a temperature of about 50.degree. C. to about 105.degree. C. for a period long enough to dissolve sufficient aluminum to produce an aqueous solution having an Al:Cl molar ratio in the range of 1.7 to 2.2:1 and an aluminum concentration of 7.5 to 13% by weight. The reaction is carried out in such a manner so that the aluminum powder is dissolved rapidly enough so that the final basic aluminum chloride has a Band III fraction of at least 20%, preferably 25%. The solution is then dried to provide a final basic aluminum chloride in a form of a hydrated powder having a Band III fraction of at least 20%, preferably 25%.
European Published Patent Applications Nos. 0 191 628 and 0 256 832 of Unilever disclose the preparation of basic aluminum halides having at least 20% of the aluminum contained in the Band III fraction for use in antiperspirants. These references disclose processes for the direct manufacture of basic aluminum halides having an aluminum/halide molar ratio of 1.7:1 to 2.2:1 from the known reaction of aluminum metal with aluminum halides. The processes require a reaction temperature of from 50 to 105.degree. C. The final aluminum concentration of the solutions is 0.8% to 6.75%. The solutions may be dried to provide a powder.
European Patent Application No. 0 274 252 of Dow discloses a process for preparing basic aluminum compounds which have a Band III percent aluminum value of at least 40%. The process comprises reacting an aluminum compound of a prescribed formula with aluminum metal in an aqueous medium at a temperature of between 50.degree. C. to 195.degree. C. until a ratio of aluminum to anion of 0.5 to 2.5:1 is obtained.
Antiperspirant compositions comprising combinations of aluminum compounds and zirconium compounds or complexes are also known in the art. For example, U.S. Pat. No. 4,017,599 of Rubino (Armour Pharmaceutical) discloses water soluble complexes of a basic aluminum compound, a zirconium compound and an amino compound. The products have an Al/Zr molar ratio of about 10:1 to 1:10. European Published Patent Application No. 0 256 831 of Unilever discloses a process for the manufacture of aluminum zirconium halohydrates, having an Al/Zr ratio of 2:1 to 7:1. The process comprises dissolving metallic aluminum halide in a zirconium-halide mixture heated to 50 to 105.degree. C. The final product has a size exclusion chromatogram of which the Band III portion is at least 20%.
However, such basic aluminum and aluminum zirconium compounds having a preponderance of Band III aluminum species and processes for the production of such compounds have proven to have a number of disadvantages, particularly in their preparation. For example, these processes generally require high heating temperatures to properly modify the basic aluminum species. This high degree of heating raises the cost of manufacturing these compounds. Moreover, in order to increase the concentration of the Band III species, relatively low concentration solutions of the starting materials need to be employed. This raises the cost of drying the solutions to powders. Also, basic aluminum compounds having a high percentage of Band III are relatively unstable in aqueous solutions at room temperature.